The functional organization of the primate retina is investigated using techniques which identify single cells or single populations of neurons. With Golgi impregnation, electron microscopy (EM), Golgi-EM, formaldehyde-induced fluorescence (FIF) for catecholamines, and immunohistochemistry, the component elements of the neuronal circuitry are identified. By these studies of the structure, connections, synapses, and neurotransmitters of Macaca retina, the functional role of neurons in the processing of the visual image in the retina can be defined. Dopamine-containing amacrine (DA) cells were localized in whole, flat-mounts of the rhesus monkey retina using FIF. Their distribution parallels that of the rod photoreceptors in a topographic pattern across the retina with peak densities of both DA cells and rods occurring at the same location. This evidence suggests a functional role for dopamine in the rod neuronal circuitry of primates. Bipolar cells, the interneurons which connect photorceptors in the outer plexiform layer (OPL) to amacrine cells and ganglion cells in the inner plexiform layer (IPL) have only been found to contact one to seven cones in the OPL. Using Golgi impregnation, a new bipolar cell type which connects to as many as three times the number of cones as the other bipolars has been identified. These giant bistratified bipolar cells also have an axon that arborizes in two separate strata of the IPL. Aside from the bistratification of this arborization, which has never been described for any bipolar cell type in primates and is rarely reported in mammalian retinas, the highly asymmetric arrangement of this axon terminal suggests it may be involved in a function other than the formation of the concentric receptive field center responses of ganglion cells.